Zinc, omega-3 fatty acids, and prostate cancer survival

A study in Sweden examining the effects of zinc and the omega-3 fatty acid DHA on mortality in prostate cancer patients was presented at the American Association for Cancer Research annual meeting in April. Five-hundred twenty-five men with prostate cancer were followed for twenty years after being diagnosed with prostate cancer.  Baseline dietary habits, stage of cancer at diagnosis, and deaths over the twenty years were recorded and analyzed.1

The authors chose to investigate these two nutrients because zinc and omega-3s share the common action of attenuating the inflammatory response, and chronic systemic inflammation may fuel prostate cancer progression. Importantly, zinc and DHA are both difficult to obtain on a plant-based diet.

Zinc is especially concentrated in the prostate, but zinc levels become depleted in cancerous cells. Addition of zinc to cultured prostate cancer cells leads to cell death, possibly by suppressing the activity of inflammatory molecules. A previous study found that long-term zinc supplementation was associated with reduced risk of advanced prostate cancer.2

In the current study, the researchers organized the study participants into quartiles according to their intakes of zinc and DHA. In men who were diagnosed at with early stage cancers, the highest quartile of zinc intake (15.7 mg zinc daily or more) was associated with a 74% reduction in risk of death from prostate cancer compared to the lowest quartile (12.8 mg zinc daily or less). Absorption of zinc tends to be low on a vegan diet – beans, whole grains, nuts, and seeds have high zinc content, however these foods also contain substances that inhibit the aborption of zinc.3 A 2009 study of vegetarians found a high prevalence of zinc deficiency.4 To correct for bioavailability, the zinc requirement for vegans may be as much as 50% higher than that of omnivores.5

I recommend zinc supplementation with a multivitamin and mineral to ensure sufficient zinc intake in vegans or those who minimize animal foods.

The connection between omega-3 intake and prostate cancer is somewhat complex. For example, flaxseed oil was found to increase prostate cancer risk, whereas whole flaxseed, EPA, and DHA were found to be protective.6,7,8 EPA and DHA are known to have anti-cancer and anti-inflammatory properties.9 In this study, the highest quartile of DHA intake was associated with 30% reduced risk of overall prostate cancer mortality, and a 45% risk reduction in men diagnosed at early stages, supporting the idea that DHA is protective against prostate cancer. Plant foods contain ALA, which can be elongated to DHA, but the major food source of DHA is fish, which often contains pollutants and is not acceptable for vegetarians and vegans. For these reasons, I recommend a laboratory cultivated DHA supplement made from micro-algae, which is also a more environmentally sustainable option than fish or fish oil.



1. Meyer MS, Kasperzyk JL, Andren O, et al. Anti-inflammatory nutrients and prostate cancer survival in the Örebro Prostate Cancer Survivors Cohort. [Abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; 2010. Abstract nr 5747

MedPageToday. AACR: Zinc Linked to Prostate Cancer Survival. http://www.medpagetoday.com/MeetingCoverage/AACR/19685

2. Gonzalez A, Peters U, Lampe JW, White E. Zinc intake from supplements and diet and prostate cancer. Nutr Cancer. 2009;61(2):206-15.

3. Hunt JR. Bioavailability of iron, zinc, and other trace minerals from vegetarian diets. Am J Clin Nutr 2003;78(suppl):633S–9S.

4. de Bortoli MC, Cozzolino SM. Zinc and selenium nutritional status in vegetarians. Biol Trace Elem Res. 2009 Mar;127(3):228-33.

5. Frassinetti S, Bronzetti G, Caltavuturo L, et al. The role of zinc in life: a review. J Environ Pathol Toxicol Oncol. 2006;25(3):597-610.

6. Brouwer IA, Katan MB, Zock PL. Dietary alpha-linolenic acid is associated with reduced risk of fatal coronary heart disease, but increased prostate cancer risk: a meta-analysis. J Nutr 2004 Apr;134(4):919-22

7. Demark-Wahnefried W, Polascik TJ, George SL, et al. Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiol Biomarkers Prev. 2008 Dec;17(12):3577-87.

8. Leitzmann MF, Stampfer MJ, Michaud DS, et al. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr. 2004 Jul;80(1):204-16.

9. Spencer L, Mann C, Metcalfe M, et al. The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential. Eur J Cancer. 2009 Aug;45(12):2077-86. 

Citrus Fruits Help Stave Off Vision Loss

Its not just citrus fruits, new findings in the journal Ophthalmology suggest older adults eating a lot of leafy greens, citrus fruits and fish are less likely to develop age-related macular degeneration (AMD), a major contributor to vision lose. Studying the diets of 4,000 adults, experts claim foods rich in omega-3s, vitamin C and E, zinc and antioxidants lower the risk of AMD. These low-sugar foods do not cause surges in blood pressure, which may harm retinas; Reuters reports.

Actually, last year researchers determined plant nutrients lutein and zeaxanthin, found in foods like spinach, kale and collard greens, promote eye health and prevent cataracts, while eating red meat 10 times week increases the likelihood of age-related macular degeneration by 47%.

In related news, a recent study showed vegetable-based diabetes offer superior diabetes control and omega-3 fatty acids, like those contained in walnuts, reduce inflammation linked to heart disease.

Image credit: Yannick .

Flaxseed Proteins Lower Blood Pressure

New research in the Journal of Functional Foods suggests flaxseeds contain amino acids that may help lower blood pressure. The study is a little complicated, but scientists determined a protein in flaxseed meal acts as an ACE-inhibitor, lowering blood pressure and reducing angiotensin. Angiotensin causes blood vessels to contract and induces hypertension. Researchers noted that these proteins have beneficial effects in the kidneys that may also help lower blood pressure; Food Navigator reports.

I eat flaxseeds everyday. Flaxseeds are potent sources of omega-3 essential fatty acids are great sources of iron, zinc, calcium, protein, magnesium, vitamin E and folate, all potent disease-fighters, but flaxseed oil is a drag. According to Dr. Fuhrman, flaxseed oil is nothing but fat and devoid of all the nutrients that make flaxseed so good. Maybe you can use it on a squeaky door.

In related news, previous research has shown salt decreases levels of nitric oxide synthase, an enzyme that reduces blood pressure and all that high blood pressure makes it hard for kids to think.

Image credit: redcherryhill

Zinc Cuts Diabetes Risk in Women

Ladies eat your zinc! Because new findings in the journal Diabetes Care claim increased intake of zinc may lower diabetes risk in women. Researchers studied 82,297 women and during the course of 24 years more than 6,000 cases of type-2 diabetes were documented and data obtained from a food questionnaire showed women with the highest average dietary intake of zinc cut diabetes risk by 10% and 8% for those with highest average total intake of zinc; NutraIngredients reports.

Peas are a good source of zinc. So are sesame seeds, with lots of zinc, calcium, magnesium, copper, manganese and fiber. Asparagus is good too. Asparagus is packed with zinc as well as selenium and folate. And other green veggies, like broccoli, kale and lettuce are also awesome sources of zinc.

Zinc is important for guys too. Previous studies show low levels of zinc contribute to cancer, cardiovascular and all-cause mortality risk in middle-aged men. Eek!

Image credit: Dayna McIsaac